1. Field of the Invention
The present invention relates to a wind turbine comprising:                a wind turbine tower        a nacelle provided on the wind turbine        a wind turbine rotor hub rotatably mounted at the nacelle, the wind turbine rotor hub having at least one wind turbine blade mounted thereon        a shaft coupled to the wind turbine rotor hub, and        a generator coupled to the shaft, which generator comprises a rotor arranged rotatbly in relation to a stator, which rotor comprises at least one superconducting rotor coil in a rotor chamber encapsulated by a rotor housing, and which stator comprises at least one stator coil of a conducting material, where the stator coil is in a stator chamber encapsulated by a stator housing; the superconducting rotor coil and the stator coil being arranged to have interacting magnetic fields for inducing a current in the stator coil when the rotor is rotated, and with a rotor-stator gap between the rotor housing and the stator housing.        
2. Description of Related Art
In this aspect, wind turbines have been used and developed. In recent developments and proposals superconducting generators have been suggested.
Superconductors are typically lighter and smaller than conventional conductors and are therefore attractive for use in wind turbines to reduce either weight or to allow for the generation of larger powers.
One example of such proposal of a superconducting wind turbine is disclosed in U.S. Patent Application Publication 2009/0224550 A1. For practical purposes and operation on-shore as well as off-shore, the disclosed superconducting wind turbine has a number of shortcomings such as the configuration and arrangement of the superconducting rotor coils and coils which is not suited for operational conditions.
Another example of such a super conducting wind turbine is disclosed in U.S. Pat. No. 4,146,804. The configuration discloses a stator assembly and a rotor assembly arranged in a generator housing in which the stator assembly and the rotor assembly are arranged in a stator casing and a rotor casing respectively. The rotor assembly is mounted on two bearings located at the end plates of the generator housing. The stator assembly comprises a plurality of stator coils wounded onto a Micarta bore seal connected to two end plates at the end. This configuration has the drawback that the Micarta plate in the turn end areas may bend outwards towards the rotor assembly or even collapse due to the pumping pressure and the oil pressure. In order to keep the air gap between the rotor casing and the stator casing as small as possible, the rotor assembly is supported by the bearings so that the rotor assembly is stabilised relative to the stator assembly and thereby allowing the air gap to be reduced. However, this support structure adds to the total weight of the generator and increases the production costs.